What goes wrong really depends. 3v motors had several design flaws which can cause a multitude of failures.
The oil pump rear cover fails and this causes low oil pressure. This can cause less pressure up to the top of the motor causing cam journal scoring. It also causes a lack of pressure to the chain tensioners which can result in timing cover damage, broken plastic chain guides, plastic debris in the oil pickup and pan and jumped time..
The original timing chain tensioner had a habit of popping the seal in the back of them causing oil and oil pressure loss. The result is loose chains, jumped time, damaged guides and cam journal scoring.
Since the phasers are at the "end of the line" so to speak. The can be damaged several ways and not necessarily related to the above issues.
Typically, the roll pins holding the trigger wheel on shear, the main pin on the rear of the phaser can also shear. Lack of oil to the phaser due to clogged oil passages, low oil pressure etc, can cause a clacking sound like a diesel makes. But this sound is mostly due to the lack of oil getting into the phasers due to low pressure, low volume, clogged VVT selenoid screens or a bad selenoid. The oil passages related to these components are very small and must be cleaned.